Dear Tom and Ray:
I just spoke to two different tire shops and got opposite answers to the same question. The right-side tire on my pickup is wearing quicker than the left. I have radial tires. I assumed it was normal, due to the way the differential works. One tire shop told me that I should be rotating in a cross pattern, while the other tire shop said that I should be rotating only front to rear. I was always told that reversing the tire rotation caused tire separation. Which answer is correct? — Eddie
Tom: Well, neither shop gave you the advice you really needed, Eddie. They should have told you that you need a wheel alignment.
Ray: Right. A right-side tire shouldn't be wearing any differently from the one on the left side. So if it is, something's mechanically wrong, and rather than rotate your tires and chew up another (now good) one, you should get that problem diagnosed and addressed first.
Tom: Depending on whether it's the front or rear right tire and what kind of suspension you have, a single tire can go out of alignment because the frame got bent in an accident, or because one or more of the suspension parts got bent or simply wore out. So the first thing you need is a good, old-fashioned four-wheel alignment — along with whatever repairs are necessary to get the wheels to actually align.
Ray: Then, once your truck is properly aligned, you can absolutely cross the tires. You can cross all of them in an "X" pattern, or you can cross just the two you move to the front. Or cross just the two that you move to the rear. If you have a full-size spare, you can add that into the rotation, cross three of them, put the spare on the right rear and toss the leftover tire in the trunk. Your options are limited only by your talent for origami and your ability to count.
Tom: There are a few exceptions. You can cross the tires only if you have the same size tires on all four wheels. If you have a muscle car, for instance, in which your rear wheels and tires are larger than your fronts, obviously, you can rotate only from side to side.
Ray: And if you have directional tires (some high-performance tires have treads that are designed to go only in one direction), you can rotate only front to back on the same side.
Tom: But for most people, tires can and should be crossed when they're rotated to even out the wear patterns and the pace at which they wear out.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk website.)